Individuals who perform intense physical exertion have long strived to improve their physical performance and recover faster. Individuals, such as professional athletes, military personnel, construction workers, and the like perform intense physical exertion on a regular basis. It is important these individuals are able to recover quickly and maintain maximum performance over an extended period of time. However, proper exercise physiological management is still lacking. Current methods fail to adequately provide electrolytes, hydration and carbohydrates in suitable proportions. Individuals continue to fail to reach maximum performance and suffer from heat illnesses, which can result in death.
The body must have proper balance of electrolytes and hydration to function properly. However, during intense physical exertion, the body is thrown out of balance. The average adult has a metabolic rate between 60 and 70 kcal/h at rest. However, during physical activity, metabolic rate increases to as much as 1000 kcal/h. The excess heat produced by the body during physical exertion is dissipated by a variety of means including radiation, conduction, convection and evaporation. In particular, evaporation occurs by vaporization of perspiration and is the most efficient means for dissipating the excess heat. Evaporation cools the body due to the latent heat of evaporation of water from the perspiration.
Perspiration contains several components including water, lactate, urea, potassium, calcium, magnesium, sodium and chloride. High rates of perspiration can lead to dehydration and loss of vital electrolytes, especially sodium, that are necessary for proper body function. In particular, appropriate electrolyte balance is required to maintain normal cell membrane potential both at rest and during activity, and therefore proper nerve and muscle function. The nervous system requires sufficient sodium levels for proper electrical signal transmission. Constant nerve impulses are required for a muscle to contract. The sodium and potassium are responsible for membrane depolarization that results in acytlecholine release from the terminal nerve endings and ultimately Ca++ release from the sarcoplasmic reticulum within the muscle cell. This subsequent increase in intracellular concentration of Ca++ causes muscle contraction. An inadequate balance of these electrolytes contributes to poor physical performance and may threaten health or even life.
Sodium loss can lead to low serum sodium concentration, hyponatremia. Hyponatremia can cause nausea and vomiting, difficulty concentrating, confusion, headache and in extreme cases, seizures and death (exercise associated hyponatremic encephalophathy—or brain swelling due to acute overdrinking). Furthermore, as discussed above, sodium is vital for proper muscle and nerve function. Another aspect of hyponatremia can lead to the inability to rehydrate, especially after several days of intense physical exertion. Sodium is required for the body to retain water. An individual can have difficulty retaining water if the individual does not properly replenish his sodium levels.
Dehydration is a process whereby an individual suffers from water loss without proper replenishment. An individual can exceed 4.0 liters of water per hour during intense physical activity. Dehydration can cause fatigue, muscle weakness, poor concentration, headaches, dizziness, decreased metabolism, increased heart rate, increased respiration, decreased urination, increased body temperature, extreme fatigue, muscle cramps, headaches, nausea, muscle spasms, vomiting, increased pulse, decrease in vision, confusion, chest and abdominal pain. In extreme circumstances, seizures, unconsciousness and death can occur from dehydration.
Failure of the body properly to thermoregulate or the lack of replenishment of vital electrolytes can lead to exertional heat illness. Exertional heat illnesses such as exertional heat stroke can occur if the body fails to properly thermoregulate itself because body temperature continues to rise. Examples of exertional heat illness include localized muscle cramps, systemic cramps, heat syncope (orthostatic dizziness), heat exhaustion, heat stroke, hyperthermia, hypovolemic hyponatremia, exercise associated hyponatremia and other syndromes. In some instances, these conditions can cause death. All persons can suffer exertional heat illnesses. However, specific groups of individuals, such as professional athletes and military personnel, are more prone to suffer from exertional heat illnesses due to environmental factors, uniforms and equipment.
Thermoregulation is a complex process that includes interaction between the central nervous system, cardiovascular system, renal and endocrine systems as well as the integumentary system. Factors which can inhibit the body's ability to properly thermoregulate include dehydration prior to physical exertion (known as hypohydration), clothing or environmental factors that inhibit evaporation of perspiration, viral or bacterial illness, history of heat illness, high body mass index, physical exertion unmatched by physical conditioning, overzealousness, lack of acclimatization, genetic predisposition factors such as malignant hyperthermia or exertional sickling and the use of alcohol, drugs, or medications. Even though it has been known that proper electrolyte replacement and hydration aides in physical performance, recovery and prevention of exertional heat illnesses, current replenishment systems still fail to obtain good results. Furthermore, it is still unknown the exact role electrolyte imbalance plays in many exertional heat illnesses. For example, while it has been shown that sodium chloride can help in the prevention of heat cramps, the exact cause of cramping is still unknown (Eichner, E. R., Sports Medicine Pearls and Pitfalls: Heat Cramps in Sports, Current Sports Medicine Reports, 2008, 7(4), 178-179). Individuals who take part in high intensity physical activity which results in high amounts of perspiration loss are encouraged to consume sports drinks to replenish water and electrolyte loss. It is known that individuals can have very different perspiration rates and compositions. The concentration of sodium in perspiration can vary from about 50 mg/L to about 2500 mg/L depending on the individual. Meanwhile, the concentration of potassium remains relatively constant. It is known that an individual's sodium concentration will be at the highest prior to the individual's becoming heat acclimated to a particular environment. As the individual becomes acclimated to the heat environment, his sodium concentration will decrease slightly. This is due to greater reabsorption of sodium in the sweat ducts.
Additionally, the perspiration rate can vary between about 0.2 liters/hour and 4.0 liters/hour. Depending on an individual's perspiration rate and sodium loss concentration, an individual can lose a significant amount of sodium during intense physical exertion. The typical sports drink, which contains approximately 100 mg of sodium, 30 mg potassium, and 15 grams of sugar per 240 mL of water, may not be appropriate for all individuals. For example, an individual with a high a perspiration rate and high sodium concentration could lose 1 liter of water, 2000 mg of sodium and 200 mg of potassium during intense physical activity. An individual would be required to drink twenty servings of this sports drink. This would result in an individual consuming 4.8 liters of water, 2000 mg of sodium, 600 mg of potassium and 300 grams of sugar (1200 kcal). In other situations, a higher loss of sodium could result in even higher consumption of water and calories. An individual would suffer from hyperhydration and hyperkalemia, while also consuming 1200 kcal of sugar. Hyperkalemia could cause muscle weakness, malaise, palpitations, and hyperventilation. Extreme hyperkalemia can cause fatal abnormal heart rhythms. On the other hand, certain individuals may have a low perspiration rate and low sodium concentration. For example, an individual may lose 0.200 liters of water, 120 mg of sodium and 25 mg of potassium. Again, the average sports drink will not properly replenish electrolytes and hydration. It has been suggested that rehydration drinks should have a sodium concentration similar to that of sweat of an individual (Maughan, R. J., Fluid and Electrolyte Loss and Replacement in Exercise, Journal of Sports Sciences, 1991, 9, 117-142). However, this is an overly simplistic solution and fails to address the problem of proper exercise physiology management. Current methods fail to address the complexity of the human body in this regard and the variance between individuals.